Conventionally, for engagement of mechanical parts, a variety of forms are adopted, for example, a fastening method by use of bolt(s), a physical joining method such as caulking, a welding method, and a chemical joining method such as an adhering method by an adhesive. For engagement of mechanical parts, there are also forms by which the parts are not completely joined.
For example, there are also mechanical parts that are spline engaged, such as a universal joint whose rotation direction is variable. For example, for engagement of a shaft, there are cases where involute spline (hereinafter, referred to as spline) is used for engagement between the shaft and the boss portion because the shaft is engaged with some degrees of freedom.
Splines allow a shaft or a shaft-like member to be engaged so as to be slidable in the axis direction and so that an axial torque is transmittable by mutual teeth fitting. A feature of splines is that they are highly strong and easy to be machined. For example, a shaft side of a spline can be fabricated by hobbing machining or by rolling. For example, the hole side of spline can be fabricated by broaching machining. For example, splines are heavily used for parts of a drive system of moving vehicles, such as a transmission.
Onto the spline formed on a shaft end of the rotation shaft that transmits power, grease is applied as a lubricant.
For example, in the grease application device described in Patent Document 1, a serrated small-diameter portion (hereinafter, referred to as serrated portion) of the shaft end portion is inserted into a blind hole that is formed by the nozzle block and the cylindrical body. Furthermore, through an annular recess portion that is formed between the nozzle block and the cylindrical body when the cylindrical body is inserted, grease is pressure-fed from a plurality of grease distribution holes that are opened in the cylindrical body. Grease is filled in the gap of the blind hole of the cylindrical body into which the serration portion is inserted. The surplus grease is discharged from a grease drain hole that is opened in the cylindrical body.
In the ultrasonic grease injection device described in Patent Document 2, the discharge portion has a circular pillar-like shape in an interior of which a plurality of discharge holes are radially formed. On an outer circumference of this discharge portion, there are formed recesses and protrusions that are extended in the shaft direction for positioning the discharge holes to a grease injection area in a roller clutch. Furthermore, this device includes an ultrasonic vibration generation portion that generates an ultrasonic vibration and transmits it to the discharge portion.
In this device, with an ultrasonic vibration being applied to the discharge portion, the flow resistance of grease significantly decreases.
In the grease application device described in Patent Document 3, into the center hole formed in a workpiece, there is inserted a first application nozzle whose outer circumferential surface has a first grease discharge hole for discharging grease. In this grease application device, there is formed a first grease pool portion that is located gravitationally below the first grease discharge hole of the first application nozzle. In this device, even if application work of grease is repeated a multitude of times and the grease remained around the grease discharge hole trickles down under its own weight, then the grease moves to the grease pool portion, and the grease having entered the grease pool portion will not spread along the outer circumferential surface of the application nozzle.